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Abstract:

An ink jet image forming method for forming an image including applying
ink to a printing paper sheet using a recording head of an ink jet
system. The ink contains a self-dispersion pigment, a polymer particle
having a glass transition temperature of 25° C. or lower, and
water and has a surface tension of 34 mN/m or less. When recording a line
image having a recording density of 600 dpi or more and 4,800 dpi or less
and a width of adjacent four pixels or more by conducting one scanning of
the recording head, an amount of an ink droplet applied from the
recording head is 0.6 pL or more and 6.0 pL or less, and an average ink
application amount per unit area in the line image is 0.3 μL/cm2
or more and 1.5 μL/cm2 or less.

Claims:

1. An ink jet image forming method for forming an image comprising
applying ink to a printing paper sheet using a recording head of an ink
jet system, wherein the ink contains a self-dispersion pigment, a polymer
particle having a glass transition temperature of 25.degree. C. or lower,
and water and has a surface tension of 34 mN/m or less, and wherein when
recording a line image having a recording density of 600 dpi or more and
4,800 dpi or less and a width of adjacent four pixels or more by
conducting one scanning of the recording head, an amount of an ink
droplet applied from the recording head is 0.6 pL or more and 6.0 pL or
less, and an average ink application amount per unit area in the line
image is 0.3 μL/cm2 or more and 1.5 μL/cm2 or less.

2. An ink jet image forming method according to claim 1, wherein the
polymer particle has the glass transition temperature of 15.degree. C. or
lower, and is formed of a hydrophilic acrylic polymer.

3. An ink jet image forming method according to claim 1, wherein the ink
further contains a water-soluble compound having a
hydrophilicity-hydrophobicity coefficient of 0.26 or more, the
hydrophilicity-hydrophobicity coefficient being defined by the following
equation (A), (hydrophilicity-hydrophobicity coefficient)-((water
activity value of 20-mass % aqueous solution)-(molar fraction of 20-mass
% aqueous solution))/(1-(molar fraction of water in 20-mass % aqueous
solution)). Eq. (A):

4. An ink jet image forming method according to claim 1, wherein the ink
has a viscosity of 6 mPas or less.

Description:

[0004] In recent years, studies have been made on use of a low-cost
general-purpose printing paper sheet having a coating layer formed
thereon as a recording medium used for an ink jet image forming method.
However, a printing paper sheet having a coating layer formed thereon has
a low ability of absorbing ink. Therefore, when a line image is formed
(recorded) on a printing paper sheet having a coating layer formed
thereon using an ordinary ink jet printer, problems arise such as
liability to line thickening or unevenness in the line image, delay in
fixing of the line image, and liability to lowering of the scratch
resistance of the line image. In particular, when small size letter are
printed, such a problem that the line blurs to make the letters unclear
is liable to arise. Further, when a line image is formed, in a system
that conducts recording by only one passage of an ink jet head, in
comparison with a multi-pass method of dividedly applying ink, such a
problem that ink droplets interfere with each other, known as "beading",
is conspicuously liable to occur.

[0005] In order to solve various problems which arise when an image is
formed on a printing paper sheet having a coating layer formed thereon,
Japanese Patent Application Laid-Open No. 2009-226715 proposes a
technology of recording an image with an ink which dries fast using an
ink jet recording apparatus including an ink drying unit.

[0006] However, it is difficult even for the ink used in the technology
proposed in Japanese Patent Application Laid-Open No. 2009-226715 to
suppress line thickening and image unevenness of a formed line image when
the ink is used in the system that conducts recording with only one
passage of an ink jet head. Further, it is also difficult to form a line
image excellent in fixability.

SUMMARY OF THE INVENTION

[0007] The present invention has been made in view of the problems of the
conventional technology. Accordingly, it is an object of the present
invention to provide an ink jet image forming method which suppresses
line thickening and image unevenness even without an ink drying unit, and
can form a line image excellent in fixability on a printing paper sheet
having a coating layer formed thereon by one passage.

[0008] The above-mentioned problems are solved by an exemplary embodiment
of the present invention described below. That is, according to the
exemplary embodiment of the present invention, there is provided an ink
jet image forming method for forming an image including applying ink to a
printing paper sheet using a recording head of an ink jet system, where
the ink contains a self-dispersion pigment, a polymer particle having a
glass transition temperature of 25° C. or lower, and water and has
a surface tension of 34 mN/m or less, and wherein when recording a line
image having a recording density of 600 dpi or more and 4,800 dpi or less
and a width of adjacent four pixels or more by conducting one scanning of
the recording head, an amount of an ink droplet applied from the
recording head is 0.6 pL or more and 6.0 pL or less, and an average ink
application amount per unit area in the line image is 0.3 μL/cm2
or more and 1.5 μL/cm2 or less.

[0009] According to the ink jet image forming method of the present
invention, even without the ink drying unit, line thickening and image
unevenness can be suppressed and the line image excellent in fixability
can be formed on the printing paper sheet having the coating layer formed
thereon by one passage.

[0010] Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

[0013]FIG. 3 is a schematic view illustrating an exemplary line type
recording head.

DESCRIPTION OF THE EMBODIMENTS

[0014] The present invention is described in detail in the following with
reference to exemplary embodiments. The inventors of the present
invention studied ink jet image forming methods which can fix at high
speed a line image having sufficient scratch resistance on a printing
paper sheet having a coating layer formed thereon without causing line
thickening and image unevenness. As a result, the inventors of the
present invention have found that, when ink containing a self-dispersion
pigment and polymer particles having a glass transition temperature of
25° C. or lower is applied under certain conditions to form a line
image, even without adopting an ink drying unit such as a forced drying
apparatus, line thickening and image unevenness are not caused. The
mechanism by which such effects are obtained is not clarified, but the
inventors of the present invention have the following assumption.

[0015] When an ink droplet is ejected from a recording head and applied to
a printing paper sheet having a coating layer formed thereon, first,
absorption of a liquid component of the ink in the printing paper sheet
begins. A printing paper sheet having a coating layer formed thereon
usually does not include an ink receiving layer. Therefore, the
penetration rate of the liquid component is extremely slow compared with
the cases of an ink-jet-exclusive paper sheet and a plain paper sheet. It
follows that, when a line image is recorded on a printing paper sheet
having a coating layer formed thereon using an ordinary ink jet printer
designed for an ink-jet-exclusive paper sheet or plain paper sheet,
adjacent ink droplets interfere with each other before the liquid
component penetrates the paper sheet to cause beading. Further, line
thickening, and image unevenness due to the coffee stain phenomenon are
caused.

[0016] On the other hand, ink used in an ink jet image forming method
according to the present invention contains polymer particles having a
glass transition temperature of 25° C. or lower. When this ink is
used to perform ink jet recording on a printing paper sheet having a
coating layer formed thereon, after an ink droplet is applied to the
printing paper sheet, a small amount of liquid is rapidly absorbed in the
printing paper sheet. Further, the polymer particles are molten to form a
film. This is thought to abruptly increase the viscosity of the ink
droplet to suppress line thickening. Further, a pigment is less liable to
move in an ink droplet. This is thought to suppress image unevenness.

[0017] Further, the ink to be used in the ink jet image forming method
according to the present invention has a surface tension of 34 mN/m or
less, and thus, wetting by the ink droplet of the printing paper sheet
and absorption of the ink droplet in the printing paper sheet rapidly
progress. This is thought to promote suppression of line thickening due
to increase in viscosity of the ink droplet and suppression of image
unevenness due to limited movement of the pigment. Further, in the ink
jet image forming method according to the present invention, the amount
of an ink droplet applied onto the printing paper sheet is 0.6 pL or more
and 6.0 pL or less. Further, the average ink application amount per unit
area in a line image is 0.3 μL/cm2 or more and 1.5 μL/cm2
or less. Application of the ink under these conditions, together with the
characteristics of the ink described above, is thought to exert
synergetic effects of the present invention.

[0018] <Image Forming Method>

[0019] A "line image" according to the present invention means an image
formed of a line having a certain length and a certain width. A line
image may be a straight line or a curved line, and may have a single
color or multiple colors. Further, a line portion of a formed image and a
line forming a letter are also included in the concept of the "line
image" according to the present invention. According to the present
invention, there is provided an ink jet image forming method for forming
a line image having a recording density of 600 dpi or more and 4,800 dpi
or less and a width of adjacent four pixels or more. In a line image
having a width of less than four pixels, dots are less liable to
interfere with each other, and line thickening is less liable to cause a
problem. Therefore, according to the present invention, a line image
having a width of four pixels or more is formed. The upper limit of the
width of a line image is not specifically limited, but the ink jet image
forming method according to the present invention is more effective in
forming a line image having a width of 6 mm (142 pixels in the case of
600 dpi and 1,134 pixels in the case of 4,800 dpi) or less. Further, the
ink jet image forming method according to the present invention is
particularly effective in forming a line image having a width of 3 mm (71
pixels in the case of 600 dpi and 567 pixels in the case of 4,800 dpi) or
less.

[0020] In the ink jet image forming method according to the present
invention, the amount of an ink droplet applied onto a printing paper
sheet is 0.6 pL or more and 6.0 pL or less. By setting the amount of an
ink droplet to be in the above-mentioned range, line thickening and image
unevenness of a formed line image can be suppressed. When the amount of
an ink droplet applied onto a printing paper sheet is less than 0.6 pL,
the location at which the ink droplet applied is liable to deviate due to
the influence of an airflow, and there are cases in which the edges of a
drawn line image are not sharp. Therefore, the amount of an ink droplet
applied onto a printing paper sheet is preferably 0.8 pL or more, more
preferably 1.0 pL or more. On the other hand, when the amount of an ink
droplet applied onto a printing paper sheet is more than 6.0 pL, the time
necessary for viscosity increase of the ink becomes longer. Therefore,
line thickening cannot be suppressed, and the fixability of the line
image is reduced. Therefore, the amount of an ink droplet applied onto a
printing paper sheet is preferably 5.0 pL or less, more preferably 4.5 pL
or less, particularly preferably 3.5 pL or less.

[0021] In the ink jet image forming method according to the present
invention, the average ink application amount per unit area in a line
image drawn with a recording density of 600 to 4,800 dpi is 0.3
μL/cm2 or more and 1.5 μL/cm2 or less. If the average ink
application amount is less than 0.3 μL/cm2, adjacent ink droplets
almost do not interfere with each other, and thus, line thickening, which
is one of the problems to be solved by the present invention, does not
occur. Therefore, it is more effective to set the average ink application
amount to be 0.4 μL/cm2 or more, and it is further effective to
set the average ink application amount to be 0.5 μL/cm2 or more.
On the other hand, if the average ink application amount is more than 1.5
μL/cm2, adjacent ink droplets interfere with each other, and a
large ink droplet is formed on the printing paper sheet. Therefore, the
time necessary for viscosity increase of the ink becomes longer, and
thus, line thickening cannot be suppressed, and the fixability of the
line image is reduced. In order to more effectively suppress line
thickening of a line image, the average ink application amount per unit
area in the line image is preferably 1.3 μL/cm2 or less, more
preferably 1.0 μL/cm2 or less.

[0022] "One passage" according to the present invention means that the
number of times the ink jet head scans is one with regard to all parts of
the line image to be formed. Specific examples of a preferred recording
apparatus for carrying out the ink jet image forming method according to
the present invention include a serial type printer (see FIGS. 1 and 2)
and a line type printer (see FIG. 3). For example, when the serial type
printer is used, a line image is formed while a recording head which
ejects ink moves in a main scan direction (direction of the arrow in FIG.
2). When the recording head reaches an end of the printing paper sheet,
the printing paper sheet is fed in a sub scan direction by the width of
the recorded line image. After that, a line image is formed while the
recording head moves in the main scan direction again (see FIG. 2). In
this way, the number of times the recording head passes is one with
regard to all parts of the line image to be recorded. Note that, from the
viewpoint of suppressing a blank portion on the formed line image, when
the recording head moves in the main scan direction and when the
recording head moves in the sub scan direction, regions (areas) which the
recording head scans may overlap by 10% or less. Further, when the line
type printer is used, ink is applied while the printing paper sheet is
fed in the main scan direction. Therefore, the number of times the
recording head passes is one with regard to all parts of the line image
to be recorded.

[0023] Further, according to the present invention, ink may be dividedly
applied insofar as a line image is formed by one passage. Specifically,
ink of the same color or different colors may be dividedly applied from
at least two nozzle arrays included in the recording head. Even when ink
is dividedly applied in this way, interference between ink droplets can
be suppressed to suppress image unevenness of the formed line image. When
ink is dividedly applied in multiple times, it is preferred that the time
difference between the first application and the last application be 200
msec or less. This allows the effect of the present invention to be
exerted more remarkably. Note that, if the time difference between the
first application and the last application is more than 200 msec, there
are cases in which line thickening of the formed line image can be
suppressed even when the constitution of the ink jet image forming method
according to the present invention is not adopted.

[0024] <Ink>

[0025] Coloring Material

[0026] A coloring material to be incorporated into the ink to be used in
the ink jet image forming method according to the present invention is a
self-dispersion pigment. The self-dispersion pigment is preferably an
anionic self-dispersion pigment. In the case of the anionic
self-dispersion pigment, an anionic functional group directly bonded to
the pigment is likely to have an interaction with the coating layer of a
printing paper sheet, as compared to an anionic polymer-dispersed
pigment. Accordingly, unevenness hardly occurs in a line image to be
formed. The anionic self-dispersion pigment is suitable also because it
obviates the need for the incorporation of a water-soluble polymer and
hence its solid-liquid separation with respect to water easily
progresses, allowing a line image excellent in scratch resistance to be
formed. Note that, the anionic functional group means such a functional
group that a half or more of hydrogen ions can be dissociated at a pH of
7.0. Specific examples of the anionic functional group may include a
carboxyl group, a sulfo group, and a phosphonic acid group. Of those, a
carboxyl group or a phosphonic acid group is preferred as the anionic
functional group from the viewpoint of the suppression of image
unevenness. Note that, when the self-dispersion pigment is used in
combination with a water-soluble compound to be described later, a
synergetic effect is exerted, with the result that solid-liquid
separation of the ink on a paper sheet progresses more rapidly to further
improve the fixability of a line image.

[0027] An ink set for forming line images with inks of a plurality of
colors basically includes black, cyan, magenta, and yellow inks. Note
that, red, blue, green, gray, pale cyan, and pale magenta inks, for
example, may be added to the ink set. The pigments contained in the inks
to be added are also preferably self-dispersion pigments.

[0028] The self-dispersion pigment is generally a pigment that has been
dispersed and stabilized without requiring a dispersant by introducing a
water-soluble functional group such as an anionic functional group to the
surface of the pigment directly or via another atomic group. As the
pigment before the dispersion stabilization, there may be used various
hitherto known pigments such as those listed in International Patent
WO2009/014242A.

[0029] As a method for the introduction of an anionic functional group to
the surface of the pigment, there may be given, for example, a method
involving performing oxidation treatment on carbon black. Examples of the
method involving performing oxidation treatment may include methods
involving performing treatment with hypochlorite, ozone water, hydrogen
peroxide, chlorite, nitric acid, or the like. Of those, self-dispersion
carbon black to be obtained by performing oxidation treatment on the
surface of carbon black with sodium hypochlorite is preferred from the
viewpoint of the suppression of image unevenness. Further, other examples
of the method involving performing oxidation treatment may include
surface treatment methods involving using a diazonium salt as described
in Japanese Patent No. 3808504, Japanese Patent Application Laid-Open No.
2009-515007, and Japanese Patent Application Laid-Open No. 2009-506196. A
commercially available pigment having a water-soluble (hydrophilic)
functional group such as an anionic functional group introduced into its
surface may be specifically exemplified by the following trade names:
CW-1, CW-2, and CW-3 (all of which are manufactured by ORIENT CHEMICAL
INDUSTRIES CO., LTD.); and CAB-O-JET 200, CAB-O-JET 300, and CAB-O-JET
400 (manufactured by Cabot Corporation). Note that, the CW-2 and the
CAB-O-JET 300 are self-dispersion carbon blacks including ionized
carboxyl groups in a certain proportion or more as the anionic functional
groups and including sodium ions as counter ions. That is, those carbon
blacks are carbon blacks having --COONa. Other specific examples of the
functional group to be introduced through surface treatment may include
--SO3H, --SO2H, and --P(═O)(OH)2. Those functional
groups are ionized in an aqueous medium in a certain proportion or more.
Accordingly, pigment particles are stably dispersed owing to repulsion of
charges. Examples of the counter ions may include: alkali metal ions such
as a lithium ion, a sodium ion, a potassium ion, a rubidium ion, and a
cesium ion; an ammonium ion; and ions derived from amines such as
methylamine, ethylamine, dimethylamine, 2-hydroxyethylamine,
di(2-hydroxyethyl)amine, and tri(2-hydroxyethyl)amine. The counter ions
are preferably a lithium ion, a sodium ion, a potassium ion, a rubidium
ion, a cesium ion, and an ammonium ion, more preferably a potassium ion,
a rubidium ion, a cesium ion, and an ammonium ion. As a method for the
exchange of counter ions of the self-dispersion pigment into desired
counter ions, there is, for example, a method involving adding, to the
self-dispersion pigment, a salt which can provide counter ions in an
amount more than the amount of anionic functional groups in the
self-dispersion pigment. Further, there is, for example, a method, as
described in Japanese Patent No. 4001922 and Japanese Patent Application
Laid-Open No. H11-222573, of repeatedly conducting the steps of
exchanging counter ions by performing the addition of an aqueous solution
containing target counter ions of interest and desalting (ion exchange
method).

[0030] The average particle diameter of the self-dispersion pigment is
preferably 40 nm or more, more preferably 60 nm or more, particularly
preferably 70 nm or more. Further, the average particle diameter of the
self-dispersion pigment is preferably 140 nm or less, more preferably 130
nm or less, particularly preferably 120 nm or less. The average particle
diameter of the self-dispersion pigment may be measured by a measuring
method involving utilizing the scattering of laser light. Specifically,
the measurement may be performed with "FPAR-1000" (trade name,
manufactured by Otsuka Electronics Co., Ltd., cumulant method analysis),
trade name "Nanotrac UPA150EX" (manufactured by NIKKISO CO., LTD., a 50%
cumulative value is used), or the like. Note that, the average particle
diameter of the self-dispersion pigment in the present invention is a
physical property value defined by a light scattering average particle
diameter, and is determined by a dynamic light scattering method in a
liquid.

[0031] As required, two or more kinds of pigments may be incorporated in
combination into one ink. The addition amount of the self-dispersion
pigment in the ink is set to preferably 0.5 mass % or more, more
preferably 1 mass % or more, particularly preferably 1.5 mass % or more
with respect to the total amount of the ink in order to provide
sufficient color developability. Further, the use of an ink containing an
excess amount of the pigment may reduce the gloss of a line image. In
order to improve the gloss of a line image, the height of a dot is
preferably reduced. To that end, the concentration of the pigment is set
to preferably 8 mass % or less, more preferably 6 mass % or less,
particularly preferably 5 mass % or less.

[0032] Aqueous Medium

[0033] The ink to be used in the ink jet image forming method according to
the present invention contains water as an essential component. The
content of water in the ink is preferably 30 mass % or more, more
preferably 95 mass % or less with respect to the total mass of the ink.
Further, water and a water-soluble compound are preferably used in
combination as an aqueous medium. Herein, the water-soluble compound
means a compound having such a high hydrophilicity that, in a mixed
liquid of the compound with water at a concentration of 20 mass %, the
compound is mixed in water without causing phase separation. Note that, a
compound that easily vaporizes to an excessive degree is not preferred as
the water-soluble compound from the viewpoint of the prevention of the
clogging of the ejection orifice of the recording head. Therefore, the
vapor pressure at 20° C. of the water-soluble compound is
preferably 0.04 mmHg or less.

[0034] The ink preferably contains a water-soluble compound having a
hydrophilicity-hydrophobicity coefficient defined by the following
equation (A) of 0.26 or more. Further, depending on the kind of paper
sheet, it is preferred to use an ink in which a water-soluble compound
having a hydrophilicity-hydrophobicity coefficient defined by the
following equation (A) of 0.26 or more and less than 0.37 and a
water-soluble compound having a hydrophilicity-hydrophobicity coefficient
of 0.37 or more are used in combination. When an ink composition using
the hydrophobic water-soluble compound having a
hydrophilicity-hydrophobicity coefficient of 0.37 or more in combination
is adopted, image unevenness is further suppressed and the scratch
resistance of an image is further improved because of the acceleration of
the vaporization of water.

[0035] The water activity value in the equation (A) is represented by the
following equation: water activity value=(water vapor pressure of aqueous
solution)/(water vapor pressure of pure water). The water activity value
may be measured by various methods, and any one of the measuring methods
may be employed. Of those, a chilled mirror dew point measuring method is
suitable. The term "water activity value" as used herein refers to a
value measured for a 20-mass % aqueous solution (25° C.) of the
water-soluble compound by the chilled mirror dew point measuring method
with "Aqualab CX-3TE" (trade name, manufactured by DECAGON).

[0036] According to Raoult's law, the rate of vapor pressure reduction of
a dilute solution equals the molar fraction of the solute irrespective of
the kinds of the solvent and the solute, and hence the molar fraction of
water in an aqueous solution equals the water activity value. However,
when the water activities of aqueous solutions of various water-soluble
compounds are measured, many of the water activities do not equal the
molar fraction of water.

[0037] A water activity value of an aqueous solution lower than the molar
fraction of water means that the water vapor pressure of the aqueous
solution is smaller than the theoretically calculated value and the
vaporization of water is suppressed by the presence of the solute. This
indicates that the solute is a substance having a large hydration force.
On the other hand, a water activity value of an aqueous solution higher
than the molar fraction of water suggests that the solute is a substance
having a small hydration force.

[0038] The inventors of the present invention have focused their attention
on the fact that the degree of hydrophilicity or hydrophobicity of a
water-soluble compound to be incorporated into an ink significantly
affects the acceleration of solid-liquid separation between the
self-dispersion pigment and the aqueous medium as well as various ink
performances. Based on such focus of attention, the inventors of the
present invention have defined the hydrophilicity-hydrophobicity
coefficient represented by the equation (A). The water activity value is
measured for aqueous solutions of various water-soluble compounds at the
same concentration of 20 mass %. Then, the measured values are converted
by the equation (A). Thus, a relative comparison of the degrees of
hydrophilicity or hydrophobicity of water-soluble compounds can be
performed even when the compounds have different molar fractions of water
owing to differences in molecular weight of the solutes. Note that, the
water activity value of an aqueous solution does not exceed 1, and hence
the maximum value of the hydrophilicity-hydrophobicity coefficient is 1.
Table shows the hydrophilicity-hydrophobicity coefficients of various
water-soluble compounds calculated by the equation (A). Note that, the
water-soluble compound is not limited to those shown in Table 1.

[0039] A water-soluble compound having a desired
hydrophilicity-hydrophobicity coefficient is preferably selected from
various compounds appropriate for the ink for ink jet recording and used.
A water-soluble compound having a hydrophilicity-hydrophobicity
coefficient of 0.26 or more to have a low hydrophilic tendency is
preferred from the viewpoints of further suppressing line thickening and
image unevenness and further improving fixability. Of such compounds, a
compound which has a glycol structure and in which the number of carbon
atoms to which hydrophilic groups are bonded is equal to or smaller than
the number of carbon atoms to which hydrophilic groups are not bonded is
preferred as the water-soluble compound. Such water-soluble compound is
considered to have a relatively low affinity for water and for a
self-dispersion pigment but have a high affinity for a coating layer of a
printing paper sheet. Accordingly, after the application of an ink
droplet to a printing paper sheet, such water-soluble compound tends to
be rapidly absorbed by the coating layer, resulting in rapid fixation of
a line image.

[0040] Trimethylolpropane is particularly preferred as the water-soluble
compound having a hydrophilicity-hydrophobicity coefficient defined by
the equation (A) of 0.26 or more and less than 0.37. Further, a compound
having a glycol structure with 4 to 7 carbon atoms is preferred as the
water-soluble compound having hydrophilicity-hydrophobicity coefficient
of 0.37 or more. Of such compounds, 1,2-hexanediol, 1,2-pentanediol, and
1,6-hexanediol are preferred. 1,2-hexanediol is particularly preferred
because it has a water activity value of 0.37 or more and a vapor
pressure at 20° C. of 5.3 Pa or less. The content of the
water-soluble compound in the ink is preferably 5.0 mass % or more, more
preferably 6.0 mass % or more, particularly preferably 7.0 mass % or more
with respect to the total mass of the ink. Further, the content of the
water-soluble compound in the ink is preferably 40.0 mass % or less, more
preferably 35.0 mass % or less, particularly preferably 30.0 mass % or
less with respect to the total mass of the ink.

[0041] Polymer Particle

[0042] Polymer particles are incorporated into the ink to be used in the
ink jet image forming method according to the present invention. The
glass transition temperature of the polymer particles is 25° C. or
lower. By using the ink containing such polymer particles, line
thickening and image unevenness are suppressed, and a line image
excellent in fixability and scratch resistance can be formed. The glass
transition temperature (Tg) of the polymer particles is limited to
25° C. or lower because the average temperature of an in-room
environment is assumed to be approximately 25° C. When polymer
particles having a glass transition temperature higher than 25° C.
are used, the polymer particles are less liable to form a film even after
an ejected ink droplet is applied to a printing paper sheet. This means
that the viscosity of the ink droplet is not abruptly increased.
Therefore, line thickening cannot be suppressed, and the fixability of
the line image is reduced. It is preferred that the glass transition
temperature of the polymer particles be 15° C. or lower. Further,
the glass transition temperature of the polymer particles is preferably
-60° C. or higher, more preferably -50° C. or higher. If
the glass transition temperature of the polymer particles is lower than
-60° C., there are cases in which the strength of the formed film
is too low. Note that, the glass transition temperature of the polymer
particles can be measured according to an ordinary method. Specifically,
the measurement can be made using a thermal analyzer such as a
differential scanning calorimeter (DSC).

[0043] The polymer particles preferably have satisfactory dispersibility
in an aqueous medium. A polymer constituting the polymer particles is
preferably a hydrophilic acrylic polymer or a hydrophilic urethane-based
polymer. The hydrophilic acrylic polymer is a copolymer obtained by
copolymerization of an acrylic monomer and any other monomer
copolymerizable with the acrylic monomer. Examples of the acrylic monomer
may include an unsaturated carboxylic acid monomer, an unsaturated
sulfonic acid monomer, an acrylic acid ester monomer, a methacrylic acid
ester monomer, and a crosslinkable acrylic monomer having two or more
polymerizable double bonds.

[0047] Further, specific examples of the monomer copolymerizable with an
acrylic monomer may include: aromatic vinyl monomers such as styrene,
α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene,
vinylanisole, vinylnaphthalene, and divinylbenzene; olefins such as
ethylene and propylene; dienes such as butadiene and chloroprene; vinyl
monomers such as vinyl ether, vinyl ketone, and vinylpyrrolidone;
acrylamides such as acrylamide, methacrylamide, and
N,N'-dimethylacrylamide; hydroxy group-containing monomers such as
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl
methacrylate, and 2-hydroxypropyl methacrylate; and unsaturated sulfonic
acid monomers such as styrenesulfonic acid and
2-acrylamide-2-methylpropanesulfonic acid.

[0048] The weight-average molecular weight of the polymer is preferably
100,000 or more and 50,000,000 or less from the viewpoints of the
ejection characteristic of the ink, print density, and scratch
resistance. Further, the weight-average molecular weight of the polymer
is more preferably 200,000 or more, particularly preferably 250,000 or
more. Further, the weight-average molecular weight of the polymer is more
preferably 10,000,000 or less, still more preferably 8,000,000 or less.
When the weight-average molecular weight of the polymer is less than
100,000, the scratch resistance of a line image to be formed may be
reduced. On the other hand, when the weight-average molecular weight of
the polymer is more than 50,000,000, the ejection characteristic of the
ink may be impaired.

[0049] The polymer particles are blended in the ink in, for example, a
state of a polymer emulsion in which the polymer particles are dispersed
in a solvent. The content of the polymer emulsion in the ink is
preferably 0.1 mass % or more and 10.0 mass % or less, more preferably
0.5 mass % or more and 5.0 mass % or less in terms of solid content with
respect to the total mass of the ink. When the content of the polymer
emulsion is less than 0.1 mass % in terms of solid content, the
fixability of a line image may be insufficient. On the other hand, when
the content of the polymer emulsion is more than 10.0 mass % in terms of
solid content, the dispersion stability of the self-dispersion pigment
may be reduced.

[0050] The mass ratio (P/B ratio) of the solid content of the
self-dispersion pigment (P) to that of the polymer particle (B) in the
ink is preferably 2.0 or less, more preferably 1.0 or less, particularly
preferably 0.5 or less. The control of the P/B ratio to the numerical
range further improves the fixability of a line image.

[0051] Surfactant

[0052] A surfactant is preferably incorporated into the ink to be used in
the ink jet image forming method according to the present invention. The
incorporation of the surfactant can provide more balanced ejection
stability of the ink. The surfactant is preferably a nonionic surfactant.
Further, of the nonionic surfactants, ethylene oxide adducts of a
polyoxyethylene alkyl ether, acetylene glycol, and the like are
preferred. Those nonionic surfactants have HLB values
(hydrophile-lipophile balances) of 10 or more. The content of the
surfactant in the ink is set to preferably 0.1 mass % or more, more
preferably 0.2 mass % or more, particularly preferably 0.3 mass % or more
with respect to the total mass of the ink. Further, the content of the
surfactant in the ink is set to preferably 5.0 mass % or less, more
preferably 4.0 mass % or less, particularly preferably 3.0 mass % or less
with respect to the total mass of the ink.

[0053] Other Additives

[0054] As required, various additives may be incorporated into the ink to
be used in the ink jet image forming method according to the present
invention for the purpose of, for example, adjusting physical property
values of the ink. Specific examples of the additives may include a
viscosity adjuster, an antifoaming agent, an antiseptic agent, an
antifungal agent, an antioxidant, and a penetrant.

[0055] Surface Tension

[0056] The surface tension of the ink to be used in the ink jet image
forming method according to the present invention is 34 mN/m or less,
preferably 33 mN/m or less, more preferably 32 mN/m or less. Further, the
surface tension of the ink is preferably 20 mN/m or more, more preferably
23 mN/m or more, particularly preferably 26 mN/m or more. By using an ink
having a surface tension in the above-mentioned range, the effects of the
present invention that line thickening and image unevenness are
suppressed and a line image excellent in fixability can be formed are
exerted at the maximum. If the surface tension of the ink is more than 34
mN/m, wetting by an ink droplet of the coating layer of the printing
paper sheet is less liable to occur, and the absorption rate of the
liquid component in the coating layer becomes lower to reduce the
fixability of a line image. Note that, the surface tension of the ink is
measured using the Wilhelmy plate method. Specific examples of measuring
apparatus for measuring the surface tension of the ink include CBVP-Z
(trade name, manufactured by Kyowa Interface Science Co., Ltd).

[0057] Viscosity

[0058] The viscosity of the ink to be used in the ink jet image forming
method according to the present invention is preferably 14 mPas or less,
more preferably 10 mPas or less, particularly preferably 6 mPas. By using
ink having a viscosity in the above-mentioned range, an ink droplet can
be ejected from a recording head of a recording apparatus such as an ink
jet printer at a high frequency with ease, which facilitates application
of the ink to the ink jet image forming method according to the present
invention in which high speed printing is performed.

[0059] <Recording Apparatus>

[0060] The recording apparatus suitably used in the ink jet image forming
method according to the present invention is one having a recording head
mounted thereon for ejecting and applying ink onto a printing paper
sheet. The method of ejecting ink of the recording head is not
specifically limited insofar as the above-mentioned ink can be ejected
therefrom. As the method of ejecting ink, a method in which pressure is
applied to ink by deformation of a piezoelectric element provided in a
pump or a flow path, a method in which thermal energy is given to ink to
generate a bubble, an electrostatic suction method in which ink is
charged to use electrostatic suction force, or the like may be used. In
the ink jet image forming method according to the present invention, any
recording apparatus including a recording head which ejects ink by any
one of such methods can be used. Further, as a method of controlling the
timing of ejecting ink, a continuous method in which ink is constantly
ejected and unnecessary ink is collected before the ink is applied to a
printing paper sheet, an on-demand method in which ink is ejected only
when the ink is desired to be applied to a printing paper sheet, or the
like may be used. In the ink jet image forming method according to the
present invention, any recording apparatus which controls the timing of
ejecting ink by any one of such methods can be used.

[0061]FIG. 1 is a schematic view illustrating an exemplary ink jet
recording apparatus having a serial type recording head. A recording head
which ejects ink in an ink jet recording system is mounted on a carriage
20. The recording head includes multiple ink ejection orifices 211 to
215. As a method of applying ink while the recording head scans once, a
method in which ink of one color is ejected from one nozzle array (ink
ejection orifices) or a method in which ink of one color or inks of
multiple colors are ejected from multiple nozzle arrays may be used. Ink
cartridges 221 to 225 include a recording head, the ink ejection orifices
211 to 215, and an ink tank for supplying ink to these ink cartridges 221
to 225. A density sensor 40 is a reflection density sensor, and detects,
in a state of being provided on a side surface of the carriage 20, the
density of a test pattern recorded on a printing paper sheet 24. A
control signal and the like are transferred via a flexible cable 23 to
the recording head.

[0062] The printing paper sheet 24 having a coating layer formed thereon
passes a transport roller (not shown) and then is picked up by a delivery
roller 25, and is conveyed in the direction of the arrow (sub scan
direction) while a conveyer motor 26 is driven. The carriage 20 is guided
and supported by a guide shaft 27 and a linear encoder 28. The carriage
20 is driven by a carriage motor 30 via a drive belt 29 to reciprocate
along the guide shaft 27 in the main scan direction. A heat generating
element (electrothermal energy converter) for generating thermal energy
for ejecting ink or a piezoelectric element (electropressure converter)
is provided in the recording head (liquid path). With the timing of
reading of the linear encoder 28, the heat generating element or the
piezoelectric element is driven based on a record signal, and an ink
droplet is ejected onto the printing paper sheet 24 to be fixed thereto
to form an image.

[0063] A recovery unit 32 including caps 311 to 315 is provided at a home
position of the carriage 20 which is provided outside a recording region.
When recording is not performed, the carriage 20 is moved to the home
position and the ink ejection orifices 211 to 215 are hermetically sealed
with the corresponding caps 311 to 315, respectively. This can prevent
clogging caused by adhesion of ink due to evaporation of a liquid
component thereof or by adhesion of foreign matter such as dust and the
like. Further, the capping function of the caps is used to prevent
ejection failure and clogging of an ink ejection orifice which is
infrequently used for recording. Specifically, the caps are used for
blank ejection for preventing ejection failure of the ink ejection
orifices. Further, the caps are used for recovery of ejection of an ink
ejection orifice in which ejection failure has occurred, by sucking ink
from the ink ejection orifice using a pump (not shown).

[0064] An ink receiving portion 33 plays a role in receiving an ink
droplet which is preliminarily ejected when the recording head passes
thereover immediately before recording operation. Further, by providing a
blade or a wiping member (not shown) at a location adjacent to the caps
311 to 315, the ink ejection orifices 211 to 215 can be cleaned. Adding a
recovery unit of the recording head and other auxiliary units to the
structure of the recording apparatus is preferred, because the recording
operation can be stabilized. Specifically, it is preferred to add to the
structure of the recording apparatus, for example, a capping unit, a
cleaning unit, a pressurizing or suction unit, an electrothermal energy
converter, other kinds of a heating element, or an auxiliary heating unit
as a combination thereof, for the recording head. Further, it is also
effective to provide a preliminary ejection mode for performing ejection
other than ejection for recording, in order to stabilize the recording
operation. Further, a recording head of a cartridge type in which an ink
tank is integrally provided may also be used. Further, there may also be
used a replaceable recording head of a chip type which can be
electrically connected to a body of the recording apparatus and to which
ink can be supplied from the recording apparatus by being mounted to the
body of the recording apparatus.

[0065]FIG. 2 is a schematic view illustrating an exemplary serial type
recording head. FIG. 2 illustrates the recording head including the ink
ejection orifices 211 to 215 illustrated in FIG. 1. Note that, in FIG. 2,
the scan direction of the recording head (recording scan direction) is
the direction of the arrow. The recording head includes the multiple ink
ejection orifices 211 to 215 which are arranged in a direction
substantially orthogonal to the recording scan direction. The recording
head ejects ink droplets at predetermined timing from the respective
ejection orifices while the recording head moves and scans in the
recording scan direction. This forms an image on the printing paper sheet
with a recording resolution based on the arrangement density of the ink
ejection orifices (nozzle arrays). Note that, the recording operation of
the recording head may be in any one of the recording scan direction and
a direction opposite to the recording scan direction.

[0066] As the recording apparatus, a full line type recording apparatus
including a recording head having a length corresponding to the width of
the printing paper sheet may also be used. As the full line type
recording head, for example, one having an increased length by arranging
serial type recording heads in a staggered manner or in parallel with one
another so as to have an intended length may be used. The recording head
may also be one recording head in which ink ejection orifices 216 to 220
(nozzle columns) which are originally long are integrally formed as
illustrated in FIG. 3.

[0067] The recording apparatus which can be used in the ink jet image
forming method according to the present invention can form a line image
having a recording density of 600 dpi or more and 4,800 dpi or less and a
width of adjacent four pixels or more. It is preferred that the recording
apparatus have a control mechanism which can, in forming such a line
image, set the average ink application amount per unit area in the line
image to be 0.3 μL/cm2 or more and 1.5 μL/cm2 or less.

[0068] <Recording Medium>

[0069] The recording medium to be used in the ink jet image forming method
according to the present invention is a printing paper sheet having a
coating layer formed thereon mainly used in offset printing, gravure
printing, or the like. The coating layer is a layer of a coating provided
on a front surface and/or a rear surface of woodfree paper or medium
quality paper, or a layer of a coating formed when the paper is made, for
the purpose of enhancing the aesthetic appearance or the smoothness of
the surface of the paper.

[0070] According to "Census of Manufactures" by Ministry of Economy,
Trade, and Industry and "Classification Table of Paper and Paperboard" in
"Paper and Paperboard Statistics Yearbook" by Japan Paper Association, a
printing paper sheet having a coating layer formed thereon is in the
category of coated printing paper and lightly coated paper in "printing
and communication paper sheets". The former has a coating layer formed
thereon by applying a coating which is about 15 g to 40 g per 1 m2
on a surface (both surfaces) of a paper sheet. The latter has a coating
layer formed thereon by applying a coating which is 12 g or less per 1
m2 on a surface (both surfaces) of a paper sheet. The coated
printing paper is further broken down into art paper, coated paper, light
weight coated paper, and other coated printing paper (cast-coated paper,
embossed paper, and the like) in accordance with the amount of an applied
coating, the method of surface treatment after the coating application,
and the like. Further, according to the glossiness of the surface it is
also classified into gloss paper, matte paper, dull paper, and the like.
The printing paper sheet to be used in the ink jet image forming method
according to the present invention may be any one of these printing paper
sheets having a coating layer formed thereon.

[0071] It is preferred that, when the entire printing paper sheet is
measured by X-ray florescence analysis (XRF), the proportion of calcium
with respect to the other elements than carbon and oxygen be 5.0 mass %
or more. By using such a printing paper sheet, interaction thereof with
the above-mentioned ink improves the coagulation rate of the pigment to
reduce the image unevenness. Note that, with XRF described above, the
amounts of various kinds of elements existing in a paper sheet having a
thickness of about 100 μm can be measured with good reproducibility by
only fixing a sample (paper) on a sample stage and applying X-rays
thereto. XRF cannot detect hydrogen, helium, lithium, and a superheavy
element which is uranium or a heavier element from the measuring
principle thereof. However, it is almost impossible that helium, lithium,
or a superheavy element which is uranium or a heavier element exists in
the paper with a proportion which is not negligible. Therefore, the
element proportion obtained by analysis of paper with XRF can be said to
be substantially the proportion of the element with respect to all
elements forming the paper except hydrogen.

[0072] The mainstream of printing today is offset printing using an
oil-based ink. Therefore, the coating layer has such a structure that a
coloring material and liquid component (in particular, a hydrophilic
liquid component) incorporated in the ink are difficult to penetrate
therein. Therefore, it is preferred to use a printing paper sheet having
a coating layer formed thereon, the coating layer having pores with an
average diameter of 0.1 μm or less and a pore volume of 0.3 mL/g or
less.

[0073] In the ink jet image forming method according to the present
invention, as the printing paper sheet having a coating layer formed
thereon, the following printing paper sheets (trade names) can be used.

[0074] Examples of the art paper may include: OK Ultra Aquasatin, OK
Kinfuji, SA Kinfuji, and Satin Kinfuji (all of which are manufactured by
Oji Holdings Corporation); Hyperpyrenee and Silverdia (both of which are
manufactured by Nippon Paper Industries Co., Ltd.); Green Utrillo
(manufactured by Daio Paper Corporation); Pearl Coat and New V Matte
(both of which are manufactured by MITSUBISHI PAPER MILLS LIMITED);
Raicho Super Art (manufactured by Chuetsu Pulp & Paper Co., Ltd.); and
Hi-Mckinley (manufactured by Gojo Paper MFG., Co. Ltd.). Examples of the
coated paper may include OK Top Coat, OK Top Coat dull, OK Top Coat
matte, OK Trinity, and OK Casablanca (all of which are manufactured by
Oji Holdings Corporation); Aurora Coat, Silverdia, and Shiraoi matte (all
of which are manufactured by Nippon Paper Industries Co., Ltd.); Green
Utrillo (manufactured by Daio Paper Corporation); and Pearl Coat and New
V Matte (both of which are manufactured by MITSUBISHI PAPER MILLS
LIMITED).

[0076] Next, the present invention is described more specifically by way
of examples and comparative examples. Note that, "part" and "%" in the
following description are based on the mass unless otherwise noted.
Further, the surface tensions of the inks were measured using a surface
tension meter (trade name "CBVP-Z" manufactured by Kyowa Interface
Science Co., Ltd.). Further, the viscosities of the inks were measured
using a viscometer (trade name "RE-80 Viscometer" manufactured by TOKI
SANGYO CO., LTD).

[0077] <Production of Hydrophilic Polymer Emulsion A>

[0078] Polymerization was performed according to an ordinary method using
styrene/n-butyl acrylate/acrylic acid of 3.0/6.0/1.5 (mass ratio), sodium
dodecyl sulfate of 0.25 (mass ratio), and potassium persulfate
(manufactured by Sigma-Aldrich) as an initiator. After the
polymerization, the resultant was neutralized with a potassium hydroxide
(KOH) aqueous solution, purified, and concentrated to obtain a
hydrophilic polymer emulsion A having a solid content of 10%. The pH of
the resultant hydrophilic polymer emulsion A was adjusted to 8.5. The
polymer particles contained in the hydrophilic polymer emulsion A had an
average particle diameter (D50) of 122 nm. Further, the polymer
constituting the polymer particles had an acid value of 101 mgKOH/g and a
glass transition temperature (Tg) of -3° C.

[0079] <Production of Hydrophilic Polymer Emulsion B>

[0080] A hydrophilic polymer emulsion B having a solid content of 10 mass
% was obtained in the same manner as in "Production of Hydrophilic
Polymer Emulsion A" described above except for using styrene/n-butyl
acrylate/acrylic acid of 7.0/2.0/1.5 (mass ratio). The pH of the
resultant hydrophilic polymer emulsion B was adjusted to 8.5. The polymer
particles contained in the hydrophilic polymer emulsion B had an average
particle diameter (D50) of 130 nm. Further, the polymer constituting the
polymer particles had an acid value of 100 mgKOH/g and a glass transition
temperature (Tg) of 58° C.

[0081] <Preparation of Inks (Inks 1 to 18)>

[0082] The components constituting inks were mixed according to
compositions shown in Tables 2-1 to 2-3 (total: 100 parts), and then
stirred for 1 hour. Next, the mixtures were filtered through a filter
having a pore diameter of 2.5 μm to prepare the inks. Note that,
"Water" in Tables 2-1 to 2-3 refers to ion exchanged water, and
"Acetylenol EH" is a trade name of a nonionic surfactant (manufactured by
Kawaken Fine Chemicals Co., Ltd.). Further, aqueous dispersions of
various anionic self-dispersion pigments shown below were used as "Kind
of pigment" in Tables 2-1 to 2-3.

[0089] Prepared inks were used to form an image on a printing paper sheet
having a coating layer formed thereon (trade name "OK Top Coat"
manufactured by Oji Holdings Corporation). Specifically, an ink tank
filled with ink was mounted on a black ink head portion of a recording
apparatus (printer), and a line image having a width of 8 pixels and a
line image having a width of 25 pixels which correspond to 1,200 dpi were
printed using a print pattern formed by uniform and random dots. Note
that, all the predetermined line images were printed by one passage.
Table 3 shows the used inks, the recording apparatus, the average ink
application amounts, and the results of evaluation of the images.
Further, the types of the used recording apparatus are as follows.

[0095] A digital microscope (trade name "Personal IAS" manufactured by
Quality Engineering Associates Inc.) was used to measure the widths of
the line images (actually measured values). Then, the difference between
the actually measured value and the width of the line image calculated
from the recording density (calculated value) was calculated, and the
line thickening of the line image having a width of 8 pixels and the line
thickening of the line image having a width of 25 pixels were evaluated
in accordance with the following evaluation criteria. Note that, the
calculated value of the width of the line image having a width of 8
pixels in a recorded product corresponding to a recording density of
1,200 dpi is 169 μm, and the calculated value of the width of the line
image having a width of 25 pixels in a recorded product corresponding to
a recording density of 1,200 dpi is 529 μm. In the following
evaluation criteria, "A" and "B" are acceptable levels, and "C" to "F"
are unacceptable levels.

[0103] The printed line images were visually observed using a loupe, and
the image unevenness was evaluated in accordance with the following
evaluation criteria. Note that, in the following evaluation criteria, "A"
and "B" are acceptable levels, and "C" is an unacceptable level.

[0104] A: Unevenness was not at all recognized, and a satisfactory line
image was formed.

[0105] B: Unevenness was slightly recognized, but a line image which
presents practically no problem was formed.

[0106] C: Unevenness was caused, and a low quality line image was formed.

[0107] Fixability

[0108] After a lapse of 20 seconds after a solid image was printed, the
solid image was rubbed once with a lens-cleaning paper sheet with a
weight of 360 g mounted thereon. The extent of fading of the ink in the
solid image was visually observed, and the fixability was evaluated in
accordance with the following evaluation criteria. Note that, in the
following evaluation criteria, "A" and "B" are acceptable levels, and "C"
is an unacceptable level.

[0109] A: No fading was recognized, and the lens-cleaning paper sheet did
not get dirty.

[0112] As shown in Table 3, when Inks 1 to 9 containing polymer particles
formed of a polymer having a glass transition temperature of -3°
C. were used, line thickening and image unevenness were suppressed, and
it was possible to record line images excellent in fixability (Examples 1
to 14). On the other hand, when Inks 12 to 15 containing polymer
particles formed of a polymer having a glass transition temperature of
58° C. and Inks 16 and 17 which did not contain polymer particles
were used, neither line thickening nor image unevenness was suppressed.
Further, the fixability was conspicuously reduced (Comparative Examples 1
to 6). Note that, the fixability of a line image recorded using an ink
having a high surface tension was conspicuously reduced (Comparative
Example 7). Further, image unevenness was caused with regard to a line
image recorded using a recording apparatus in which the amount of an ink
droplet ejected was large (Comparative Example 8).

Image Forming Method B

Examples 15 to 17 and Comparative Example 9

[0113] Prepared inks were used to form an image on a printing paper sheet
having a coating layer formed thereon (trade name "OK Top Coat"
manufactured by Oji Holdings Corporation). Specifically, two ink tanks
filled with ink were mounted side by side in adjacent ink head portions
of the above-mentioned recording apparatus (printer). Note that, when
different types of inks were used, the respective inks were filled in
separate ink tanks. The same amount of inks were ejected from the two ink
tanks so that the average ink application amount was as shown in Table 4,
and a line image having a width of 8 pixels and a line image having a
width of 25 pixels which correspond to 1,200 dpi were printed using the
print pattern formed by uniformly and random dots. Note that, all the
predetermined line images were printed by one passage. Further, the
"average ink application amount" shown in Table 4 is the total amount of
the applied inks. Table 4 shows the used inks, the recording apparatus,
the average ink application amounts, and the results of evaluation of the
images.

[0114] As shown in Table 4, also with regard to line images recorded by
ejecting inks from the two ink tanks, line thickening and image
unevenness were suppressed, and it was possible to record line images
excellent in fixability (Examples 15 to 17). On the other hand, when
recording was performed with the average ink application amount being
increased, it was apparent that neither line thickening nor image
unevenness was suppressed and the fixability was conspicuously reduced
(Comparative Example 9).

[0115] While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0116] This application claims the benefit of Japanese Patent Application
No. 2012-042805, filed, Feb. 29, 2012, which is hereby incorporated by
reference herein in its entirety.